This proposal focusses on definition of the critical differences underlying fertility and infertility after vasovasostomy, and the analysis of immunodominant post-vasectomy sperm autoantigens using monoclonal antibodies and gene cloning. In most of the experiments, rats will receive a bilateral vasectomy and a later vasovasostomy, a vasectomy alone, or sham operations. Among our previous observations in this model were testicular and epididymal alterations, correlations between antisperm antibodies and reproductive tract changes, and definition of immunodominant sperm autoantigens post-vasectomy and vasovasostomy. Some vasectomy-induced responses were not reversed by a subsequent vasovasostomy. The first aim of the proposed work is to determine the basis for differences in fertility after vasovasostomy, utilizing Lewis and Fischer strains of rats, which differ dramatically in fertility after vasovasostomy but share histocompatibility loci. The second aim is to identify the types of leukocytes that appear within the reproductive tract in reaction to vasectomy and vasovasostomy using immunohistochemical studies. The third aim is to capture rat monoclonal autoantibodies to dominant post-vasectomy sperm autoantigens by constructing rat x rat hybridomas. The fourth aim is to clone and sequence cDNAs for the dominant post-vasectomy sperm autoantigens, to characterize the autoantigens, and the utilize the nucleotide and protein probes thereby made available for further studies in rats and humans. Methods include light and electron microscopy, immunohistochemistry, determination of serum antisperm autoantigens, micropuncture for measurement of intraluminal hydrostatic pressure, and determination of the resistance of the vas deferens to fluid flow. Standard methods of molecular biology will be employed to clone cDNAs and analyze recombinant sperm autoantigens.